Optoelectronics Circuits Manual, 2nd Edition

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Basic LED display circuits

The simple LED (light-emitting diode) is the most important and widely used of all modern optoelectronic devices. It emits a fairly narrow spectrum of visible (usually red, orange, yellow or green) or invisible (infra-red) light when its internal diode junction is stimulated by a forward electric current, has good power-to-light energy conversion efficiency, and has a very fast response time (often less than 0.1µs). This chapter explains LED operating principles and characteristics and shows a variety of ways of using LEDs as basic visual indicators, as simple ‘flashing light’ displays, and as micropower flashing lights.

LED basics

Introduction

Figure 2.1(a) shows the standard symbol used to represent a LED in ...